The invention relates to a method and apparatus for mechanically stacking sectioned bar stock (hereafter referred to as sections) in layers, such sections arriving in groups or even separately and being optionally turned over or not turned over for further delivery and stacking. German Patent Specification No. 1,556,235 discloses a system for stacking sections in which the entire operating sequence from the infeed of the sections to stacking takes place completely automatically. In this system, the sections may be supplied in any desired sequence. The sections are separated from one another (individualized) and, as required, are individually and successively turned over and are subsequently individually stacked. Accordingly, in addition to performing a vertical lifting motion, the stacking table must be traversed in the horizontal plane by one section pitch after each section has been deposited. The construction and control of the stacking table is therefore very expensive. In one embodiment, each section is individually stacked by means of lowerable hoisting magnets with strippers; a substantial amount of time would be required for transferring each section to the stacking table because the stacking table must remain stationary for a substantial part of this time.
In order to achieve a shorter delivery time, in another embodiment of the same Patent Specification, the sections are ejected by stripping from a stationary permanent magnet. Ejection from a certain height however readily causes damage and is hardly suitable for sections of large cross-section.
German Patent Specification No. 1,198,287 discloses a stacking device in which the sections may be delivered unturned as well as turned-over. In this device, stacking magnets are pivotably supported on arms which are vertically and horizontally movable. To stack an unturned layer, the stacking magnets are lowered from above on to the sections, which lie on a feeder conveyor, and after energising the stacking magnets, the sections are raised, are moved over the stacking table and are lowered. To stack a turned-over layer, the stacking magnets are rotated through 180.degree. about a horizontal axis, and are lowered below the feeder conveyor plane. A group of sections is then moved over the stacking magnets and when these are raised, the sections are also raised from the feeder conveyor, after which the stacking magnets are rotated back, moved over the stacking table and lowered. These three different movements require an expensive construction. Moreover, a very complex control system is required because of the different movements which the stacking magnets perform when the layer of sections is turned over and when the layer is not turned over. Furthermore, the amount of time required for each operating cycle is very large because of the series of successive movements, and therefore a device of this kind is not able to achieve a large rate of throughput.